TITLE:         Palmer Station, Antarctica  (LTER REPORT)
AUTHOR:        Raymond C. Smith and Karen S. Baker (contributed article)
JOURNAL/BOOK: The Climates of the Long-Term Ecological Research Sites
EDITOR:       David Greenland
              [PENDING]
         
1. Site Description
The Palmer LTER study area is located to the west of the Antarctic Peninsula 
and centered on the region which surrounds Palmer Station (64deg 40'S,
64deg 03'W).  Palmer Station (Fig. 1) is located in a protected harbor on 
the southwest side of Anvers Island midway down the Antarctic Peninsula.  
This study area is representative of a polar marine biome and research
is focused on the Antarctic pelagic marine ecosystem, inclusive of marine 
sea ice habitats, regional oceanography and terrestrial nesting sites of 
sea bird predators.  A sampling grid, motivated by the need for station
locations that could be visited repeatedly over time scales of many
years, has been established along the west coast of the peninsula.
This grid, which is 200 km on/offshore and 900 km along shore roughly
parallel to the peninsula, reflects the regional scale of atmospheric,
oceanic and sea ice interactions with populations in the marine ecosystem. 
Embedded within this grid are smaller scale grids addressing local 
hydrography, near shore primary and secondary production and the foraging 
ranges of the predators (seabirds) nesting near Palmer Station.

Quality meteorological data records for the Antarctic are relatively
short, most dating from the International Geophysical Year of 1957-58.
Prior to the 1905's few data were collected south of 45degS.
A consistent digital weather record is available for Palmer Station 
beginning in 1989 including daily maximum and minimum air temperature, 
wind speed and wind direction (Baker and Stammerjohn, 1995).  Measurements 
are made four times per day.  Monthly temperature data summaries for Palmer 
are available, with some gaps, back to 1974.  British Antarctic Survey 
(BAS) data from Faraday Station (Jones, 1987), located 35 nautical miles 
(65 km) south of Palmer Station, provide high quality continuous data from 
the early 1940's.  These data are highly correlated with the shorter Palmer 
record, and are used to provide a climatology for the western Antarctic 
Peninsula (WAP) area (Smith et al, 1996).

Two Automatic Weather Station (AWS) (Bromwich and Stearns, 1993) sites 
near sea level were designated at the request of the Palmer LTER program.  
AWS Bonaparte (64deg46'S, 64deg04'W) was installed in January 1992 on a 
rocky point (Fig. 2) at the entrance to Arthur Harbor about 750 m WSW of
Palmer Station.  AWS Hugo (64deg58'S, 65deg40'W) was installed in
December 1994 on an island in the Victor Hugo archipelago, a small
group of low lying islands and rocks, approximately 90 km northwest of
the Peninsula and roughly this same distance WSW of Palmer Station.
AWS Hugo, being 90 km seaward of the peninsula, is an especially
important addition since there is a sharp on/offshore gradient in
maritime versus continental regimes.  Data from AWS Hugo illustrate
the distinction between data from coastal stations, which comprise our
only historical records, and data from oceanic stations, which are
more closely coupled to the marine environment.

2. Vegetation
Phytoplankton production plays a key role in this so-called high-nutrient, 
low-chlorophyll marine environment. Factors that regulate production 
include those that control cell growth (light, temperature, and nutrients) 
and those that control cell accumulation rate and hence population growth 
(water column stability, grazing, and sinking).  Climatic factors and sea 
ice mediate several of these factors and frequently condition the water 
column for a spring bloom which is characterized by a pulse of production 
restricted in both time and space.  The abundance and distribution of 
terrestrial vegetation (predominately lichens and mosses) is sensitive to 
climatic conditions and is limited by the short growing season and the 
limited area of soil/rock substrate.  Terrestrial plant vegetation is 
thought to have relatively little influence on the marine environment.

3. Synoptic Climatology
The western Antarctic Peninsula (WAP) area is distinguished by a weather 
system that displays extreme seasonal and interannual variability.  The 
Antarctic Peninsula is a physical barrier to tropospheric circulation which 
is reflected in the sharp contrasts between the relatively mild maritime 
climate to the west and north of the peninsula and the harsher more 
continental climate to the east and south.  Further, the Peninsula is one 
place on the continent where the axis of the circumpolar low-pressure 
trough or atmospheric convergence line (ACL) crosses over land.  The 
variability of the mean position of cyclones, as the ACL seasonally and 
interannually shifts along the Antarctic Peninsula, strongly influences 
winds, temperature and the distribution of sea ice.  Weather patterns at 
Palmer are strongly influenced by the linkages between cyclones, 
temperature and sea ice extent and these patterns continually shift 
between the influence of maritime as contrasted with continental climatic 
regimes.

The climate is typically maritime Antarctic, relatively warm and moist
compared to other locations in Antarctica yet cold and dry compared to
lower latitude sites.  The temperature at Palmer is relatively mild
for the Antarctic, averaging about -10C in July/Aug and 2C in January,
with temperature extremes recorded at -31C and 9C.  Snow and rain are
common any time of year with annual rainfall averaging about 50 cm and
snowfall about 35 cm.  Values from the longer Faraday Station record
are comparable.

In polar regions wind is a dominant meteorological variable.  Storms
are evaluated in terms of wind speed and direction.  Surface wind is
decisive for the chill factor along with temperature, the drift and 
compaction of sea ice, the depth of the ocean upper mixed layer. Further,
wind greatly influences the overall conditions for human activity.  The 
WAP experiences the mildest and wettest climate of the Antarctic
influenced both by relatively warm winds from the northwest quadrant
and cold dry continental conditions with winds from the southern
quadrants.

A predominant and distinguishing characteristic of the Southern 
Ocean is sea ice, with a range of minimum to maximum sea 
ice cover that represents the largest seasonal surface change 
(roughly 16x10^6 km2) on earth.  The LTER region is distinguished 
by an annual sea ice cycle showing a relatively short period of ice 
advance (about 5 months) followed by a longer period of ice retreat 
(7 months) and a long-term persistence, wherein two to four high-ice 
years are followed by one to three low-ice years.  An oscillation of
high and low-ice years has been linked to the Southern Oscillation
Index.  

4. Water Balance
In spite of their importance for completion of water, salt and heat
budgets of the ocean, values for evaporation and precipitation over
the ocean are not well determined.  Typically their estimation depends
upon various extrapolative schemes using data from islands and coastal
areas.  To the best of our knowledge there are few, if any, reliable
data for the WAP area.

5. Climatic Factors Affecting Flora and Fauna
Factors strongly influencing the flora and fauna of this site
include: low temperatures, a short growing season, high winds 
influencing the depth of the mixed layer, proximity to land with 
the potential for input of micronutrients, and the presence or 
absence of sea ice and snow cover.  Sea ice is associated with a 
range of predator and prey habitats and is hypothesized to play a 
key role in various trophic level couplings.  The high variability 
in ice coverage in the vicinity of Palmer Station provides the LTER 
with an ideal study site in which to conduct "natural experiments" 
associated with high interannual sea ice variability and hypothesized 
consequences to the marine ecology of the area.

6. Notes on Climate Data
The climate record at Palmer Station itself is too short for developing 
a 30 year climatology.  Meteorological data from the British Antarctic 
Survey (BAS) is available for Faraday Station since the mid 1940's.  
Comparison for the period overlapping data from 1974 to 1991, shows the 
Palmer record has a similar seasonal pattern but is on average 1 to 3degC 
higher than the Faraday temperature record (Smith et al, 1996).  
Taking into account the serial correlation present in the data, there 
is a significant correlation between monthly mean air temperatures 
from 1974 to 1991 where
     Temperature(Palmer)=1.15+0.96*Temperature(Faraday)
with N=188 and R2=0.94 so that the Faraday temperature data may be 
used as a proxy for Palmer Station.

7. Literature Cited
Smith, R.C., S. Stammerjohn, K.S. Baker, 1996 
Surface air temperature variations in the western Antarctic peninsula
region, in Foundations for Ecological Research West of the Antarctic 
Peninsula AGU Antarctic Research Series, R.M. Ross, L.B. Quetin,
E.E. Hofmann (eds)

Baker, K.S. and S. Stammerjohn, 1995 (accepted)
Palmer LTER: Palmer Station weather records, Antarctic Journal

D.H. Bromwich, and C.R. Stearns (Eds.), Antarctic Meteorology and
Climatology: studies based on automatic weather stations, American
Geophysical Union, New York, 1993. 207pp.

Jones, P.D. A Data Bank of Antarctic Surface Temperature and Pressure
Data, Office of Energy Research, Office of Basic Energy Sciences, Carbon
Dioxide Research Division, Washington D.C., 1987.

FIGURES
fig1-photo1 (areal palmer)
fig2-photo2 (aws-bonaparte)
tbl1-Palmer Station (from Faraday Station) summary statistics
fig3 Palmer Station (from Faraday Station) precip vs months 1961-1990
fig4 Palmer Station (from Faraday Station) temp(max,avg,min) vs months 1961-1990